For many years, automated lumber sorters have been used in most high-production sawmills rather than manually hand pulling the lumber. These sorters can have from as few as 10 to 12 sorts up to 75 plus sorts. Since the bay centers are between 30 inches and 4 to 6 feet in width, the sorters can be quite long. The lumber must be conveyed down the lumber transport system in order to be sorted or “dropped” into the appropriate bay. Several types of lumber transports have been used in the past. The lumber transports all involve some sort of overhead chain conveying system, either dragging, pushing, or carrying the boards.
An example of a lumber sorter apparatus and how the sorter works is disclosed in U.S. Pat. No. 5,934,480, the complete disclosure of which is incorporated herein by reference.
One type of lumber transport system uses a lumber drag chain system. This system has been used for many years, mostly in the southern U.S. by companies such as HEMCO, Hi-Tech Engineering and Baxley Equipment Company. In this system, lumber is dragged down the conveying system, generally on plastic skids, by multiple strands of overhead chain with spaced apart lugs. The lumber is then tippled into the appropriate bay by a pneumatically operated device called a tipple.
FIGS. 6-8 [prior art] generally show a prior art drag chain 1 having inner metal chain links 44, outer metal chain links 42, and pins 46 connecting the inner and outer metal chain links. Each chain link has an outer surface 41, a top side surface 45, and a bottom side surface 43. A plurality of spaced-apart lugs 40 each extend from the bottom of an associated metal chain link. The lug 40 has a first surface 47 that is substantially parallel to the outer surface 41 of the associated metal link. The lug 40 has a lumber contacting side surface 49 and a second side surface 51 opposite the lumber contacting side surface 49. While the lug 40 is shown in the drawings being attached to an outer chain link, the lug 40 can be attached an inner chain link as desired. The connection between the lug 40 and the chain link can be any as desired, such as welding. Alternatively, the chain link can be integrally formed with the lug 40. The lug 40 is usually about 1.5 inches wide, 0.25 inches thick, and 5.75 inches long, but can be narrower, thicker or longer as desired for the particular lumber products being run. An example of a suitable chain is a 81X, in which the links have a pitch of 2.609 inches and a height of 1.125 inches. However, any size chain can be used as desired for the particular lumber dragging application. The direction of the chain flow during use is shown by arrow 3.
As shown in FIGS. 2, 7 and 8 [prior art], the prior art drag chain utilizes lug guards 10 to prevent unwanted contact between the lug 40 and lumber. FIG. 2B is a cross-section of the lug guard 10 at the location of weld hole 12. The weld hole 12 is constructed and sized to receive a weld washer 71. The lug guards 10 are typically formed from a plastic, such as ultra high molecular weight polyethylene. The lug guards 10 are held in place by two metal weld washers 71 that are disposed in weld holes 12 and are welded to the lug 40. The lug guard 10 extends beyond the lumber contacting side surface 49 to prevent the lumber from contacting the lumber contacting side surface 49 during use. The lug guard 10 requires at least two weld washers 71 to prevent unwanted rotation of the lug guard 10. The lug guard 10 utilizes rounded corners 14.
As shown in FIGS. 1, 7 and 8 [prior art], the prior art drag chain also generally utilizes guards to prevent unwanted contact between the lumber and the chain, hereinafter referred to as chain guards 2. FIG. 1B is a cross section of the guard 2 at a location of the hole 4. To mount the chain guard 2, two pins 46 must be removed from the chain, i.e. the chain must be broken, and the pins 46 replaced with longer connecting pins 50, washers 54 and cotter pins 52. The chain guard 2 has two holes 4, through which the longer connecting pins 50 are disposed. The chain guard 2 extends beyond the bottom side surface 43 of the metal chain link to prevent lumber from contacting the chain during use. The chain guard 2 has generally square corners 6, which tend to snag the lumber during use.
The drag chains typically have opposing pairs of lugs 40, lug guards 10, and chain guards 2 at each location, as shown in FIG. 8 [prior art]. Prior art methods of applying the lug guards 10 and chain guards 2 are expensive and the required down time is extensive to field install the guards on existing equipment. There is a great need for a more economical and faster method for installing lug guards 10 and chain guards 2.